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  • One computer on network no longer able to see gateway

    I have a strange situation that I would appreciate some guidance with.

    We have a client with a very simple network - SBS2003 - and all has been fine for years. Recently one of the computers on the network found they could access everything on the network except the internet (i.e. the gateway). Everybody else was fine. I couldn't find anything obvious but changed the gateway address from .1 to .254 and that solved the problem. One month later and another computer has the same problem ... cannot route to the gateway (on .254).

    Using ipscan on the machine finds all IPs except the gateway.
    I have scanned the computer (using Sophos) and found nothing.
    They use DHCP so all computers get the same options (subnet mask, router, DNS etc.)

    I have run out of ideas, but wondered whether someone else could give me some ideas.

    Thanks

    Colin
    Colin

  • #2
    Re: One computer on network no longer able to see gateway

    you probably checked it already, but just guessing here...

    Try to compare the route table info from that machine with another one.
    using the 'route print' command.

    Maybe something there can help you.
    Semper in faecibus sumus, sole profundum variat

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    • #3
      Re: One computer on network no longer able to see gateway

      Yup - that was one of the first things I looked at. Looks the same as all the others which work fine.

      That is what is so weird, It all looks fine but try and ping the gateway and no dice.
      Colin

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      • #4
        Re: One computer on network no longer able to see gateway

        Could you post your DHCP scope range and options?
        Regards,
        Jeremy

        Network Consultant/Engineer
        Baltimore - Washington area and beyond
        www.gma-cpa.com

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        • #5
          Re: One computer on network no longer able to see gateway

          Address pool: 192.168.1.33 - 192.168.1.50 /24 (8 hour lease)
          Router 192.168.1.254
          DNS Servers: 192.168.1.10
          WINS Server: 192.168.1.10 (0x

          SBS2003 server is 192.168.1.10

          10 users using DHCP - all but one working fine. Problem computer was fine until a week ago, now can't reach the router.
          Colin

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          • #6
            Re: One computer on network no longer able to see gateway

            What kind of router/firewall do you use? Is it licensed on a "per user" basis?

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            • #7
              Re: One computer on network no longer able to see gateway

              It is a Zywall with unlimited users. Reasonable idea though.

              Maybe I haven't been absolutely clear. The problem is not that this user cannot access the gateway - the computer cannot ping the IP (yes the FW is set to respond to ping on the LAN) ... it just doesn't see it on the network even though the routing looks fine (identical to all the others that are working) and this machine was working okay until recently.

              No new software has been installed, anti-virus is up to date etc.

              Thanks

              Colin
              Colin

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              • #8
                Re: One computer on network no longer able to see gateway

                Hi colinjack ,

                Just out of curiosity, what does the arp table look like on your clients when they try to connect to the gateway? Can the gateway ping the clients? What does the arp table on the router show for clients if it can ping on of them?

                Ryan

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